1. Field of the Invention
The field of the present invention relates to an automatic sliding doors and control/security systems therefor, particularly well suited for use in walk-in freezer or refrigerator units.
2. Background
In the past, doors used on walk-in freezer and refrigerator units have often been swinging-type doors that need to be manually opened and closed. However, manual operation of freezer or refrigerator doors can be quite inconvenient, especially when there is a large amount of traffic passing into and out of the walk-in freezer or refrigerator unit, or when persons needing access to the walk-in freezer or refrigerator unit are laden with trays or other bulky items which need to be set aside to allow manual opening of the door, followed by the extra effort of re-lifting and balancing the trays or other bulky items.
Swinging-type doors can also be hazardous to persons in close proximity to the doors, when passers-through open the doors suddenly as they enter or exit the freezer or refrigerator unit. The swinging of the door can cause serious physical harm to persons, or knock trays of food or fragile items out of their hands.
Sliding doors have been designed for use in walk-in freezer or refrigerator units. Generally, such sliding doors have been motor-driven, but require manual activation, such as by pulling on a cord or pushing a button. Such manual operation of refrigerator or freezer sliding doors can be inconvenient to persons carrying items or pushing heavy carts. Further, particularly since refrigerator or freezer doors are often large, thick and heavy, the motors used to open and close such sliding doors are generally gear-driven or hydraulic in nature, and are prone to wear and tear.
Automatic swinging doors and sliding doors have been used in supermarkets and similar environments. Sensors are typically used in automatic door systems to assist the control electronics in determining when to start or stop opening the doors. Typically, a small mechanical switch known as a microswitch is employed to indicate the stopping point for the doors. The motor drive mechanism drives the doors past the microswitch which, when the door passes, physically switches, causing an output electrical signal indicating that the door is passing. When the controller receives the microswitch signal, it commands the motor drive to stop the motion of the door. Microswitches are generally mechanical in nature, and are required to be physically moved a slight distance (e.g., by the passing of the door) in order to produce an output signal. Being mechanical in nature, microswitches are prone to wear and tear, and deterioration over time.
Other means that have been used to control the opening and closing of automatic doors are proximity detectors. Proximity detectors are generally capacitive or inductive in nature, operating on the presence or absence of a magnetic field.
Designing doors for walk-in freezer and refrigerator units involve special challenges due to the effects of the cold environment on equipment and the door structure and components. Thus, sliding doors used in supermarket environments generally are not suitable for use in walk-in freezer or refrigerator units. Further, a wide variety of safety concerns exist in the walk-in freezer or refrigerator environment which are not present, or are less present, in the supermarket environment. For example, due care must be taken to avoid the possibility of persons being trapped inside a walk-in freezer or refrigerator unit due to failure or locking of the door mechanism.
There is a need for an automated door that is particularly well adapted for use in walk-in freezer or refrigerator units. There is further a need for such an automated door system that provides a high degree of safety for users, and prevents to a maximum degree obtainable the possibility that persons may become inadvertently trapped inside a walk-in freezer or refrigerator unit.
The invention provides in one aspect an automatic sliding door system especially well suited for use in walk-in freezer or refrigerator units. In one embodiment, an automatic sliding door system includes an exterior sensor unit for detecting opening conditions on the exterior of a walk-in freezer or refrigerator unit, and an interior sensor unit for detecting opening conditions in the interior of the walk-in freezer or refrigerator unit. Each sensor unit preferably comprises both a motion sensor and a presence detector. The motion sensor detects motion towards the sliding doors, and opens the doors as they are approached. Once motion is detected, the motion sensor is preferably operated so as to track the motion no matter whether towards or away from the door, and keep the doors open so long as the motion is present. The presence detector of each sensor unit detects a change in the ambient conditions directly underneath the doorway, and keeps the door open when the ambient conditions change. In one aspect, the presence detector provides a redundant backup in case the motion sensor fails.
In a preferred embodiment, the presence detector has an autolearn capability so that, as the environmental conditions change, the presence detector relearns the characteristic environmental conditions, and does not thereafter cause the opening of the sliding door unless those conditions change.
In another aspect of the embodiments described herein, a bi-parting door comprises right and left side doors that are opened and closed simultaneously and in synchronism using a pulley mechanism connected to both the right and left side doors. The right and left doors each preferably have grooved overhead roller wheels which are guided by a track. The pulley mechanism includes a pulley connected between two pulley wheels. The right side door connects to one side (e.g., the far side) of the pulley, while the left door connects to the other side (e.g., the near side) of the pulley. When the pulley turns one direction, the doors open, and when it turns the opposite direction, the doors close. A brushless DC servo motor is preferably employed to rotate one of the pulley wheels and thereby move the pulley for opening and closing the doors. Optical sensors are deployed above one door (or, alternatively, both doors) to provide positional information to a controller, which commands the motor to operate forward or backward in either a steady or decelerating manner. The optical detectors are positioned at selected locations so as to indicate deceleration and stopping points for the doors, whether opening or closing.
In a further aspect of various embodiments as described herein, special safety and security features are provided for an automatic sliding door system. A manual push plate or pushbutton located on the interior of the walk-in freezer or refrigerator unit allows manual override and egress should the interior sensor unit fail. A key lock on the exterior of the unit allows the system to be de-activated externally, while still operative internally, to prevent persons from being trapped inside the walk-in freezer or refrigerator unit. A multi-tier alarm system is provided, which includes different alarm levels based on different conditions.
Further enhancements, variations and modifications of the above illustrative embodiments are also described in more detail herein.